I've always found it difficult, if not impossible, to get Xbox360 to detect Media Center that's on a different Gateway, even if it's on DMZ.
Try enabling UPnP [universal plug & play] on your routers, for one. Another, you may consider making one or more of the routers a switch or repeater instead of each being routed individually.
Sounds like some unnecessarily complicated stuff you have going on there. You need to get down to L-C-D [Lowest Common Denominator]. Obviously, if you plug the Xbox360 directly into a router that the PC happens to be on, WMC works 100%.
[I mean, why the hell do you wire your internet connection like that? And D-Link ... ugh! But maybe I can help?]
All you have to do is get the official MS wireless adapter and you should be up-and-running. [And there are wireless gaming repeaters that are wired, specifically for the purpose of what you are stating -- Buffalo tech, and others -- but why add that many complicated hurdles, needlessly?]
Are you running DD-WRT? I may be able to walkthru some other BS. Why not just plug the wireless gaming adapter into the console you are using at the time?
This post has been edited by SigmaXIX: Dec 31 2007, 03:49 AM